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Trouble Shooter

Honda’s Civic was a late arrival at the coil-on-plug party, and many Civics with distributor ignition systems are still soldiering on. You may need to dust off some old skills when their reliability falters.

Secondary Losses

I am working on a 2000 Honda Civic that has about 125,000 miles on it. It has a 1.6L fuel-injected engine and a four-speed automatic transmission. The vehicle arrived at our shop behind a tow truck after the owner was unable to get it started. A quick inspection revealed that the engine was completely flooded with gasoline and the spark plug center electrodes were worn to the nubs. I’d be surprised if they had ever been changed during the past ten years. The car does not belong to a regular customer and looks like it has had very little in the way of routine maintenance.

I confirmed that the engine was producing spark; ignition voltage was between 7 and 10kV while cranking. I dried out the cylinders, added a small amount of ATF to each, then installed new spark plugs. I cranked the engine but it still wouldn’t start. I removed the new plugs and found they were wet with gasoline. I checked cam timing (okay), then compression. Compression was 115 psi on cylinder 1, 100 on cylinder 2, 115 on cylinder 3 and 70 on cylinder 4. Cylinder 4 seemed low, but I attributed that to the cylinder walls being washed down with gasoline. Even with low compression in one cylinder, the engine still should have started.

The engine was obviously getting plenty of fuel, but I decided to check fuel pressure next. Pressure was 40 psi and the fuel smelled normal. I also checked the engine and chassis grounds (good). I tried drying out the engine a second time, then unplugged the injectors and used a small amount of starting fluid to try to start the engine. No luck. I removed the pre-cat oxygen sensor in case the exhaust was restricted. Still no go. Suggestions?

Ken Llewellyn

Berwyn, IL

I believe you were pretty close to finding the solution when you checked for spark, Frank. Just because an engine is producing some spark doesn’t necessarily mean it’s producing enough spark. Your measured coil output voltage of 7 to 10kV doesn’t sound like it going to be nearly enough to get the engine started. Let’s look at what may have caused the coil to weaken and fail.

The first thing to consider are the worn spark plugs you originally found in the engine. Worn plugs with extremely large gaps force the coil to work extra hard nearly all the time, rather than only occasionally under increased engine load. The coil has to produce nearly peak kV for every firing event, just so it can produce a spark that’s strong enough to jump the too-wide plug gap. Add engine load to the equation and the coil simply runs out of energy to get the job done. A steady diet of full-time peak output could cause even a relatively new coil to fail. Forcing a 10-year-old coil to do the job is something like throwing an old duffer on a treadmill, then increasing the load until his heart gives out.

Take a good look at the components inside the distributor. Are you certain you’re the first one to open up the distributor? Careless or incorrect service procedures by a previous tech may also be responsible for the vehicle’s starting problems. Perhaps the ignition coil or igniter had been previously replaced.

Honda uses a combination of spade terminals and/or eyelet terminals to connect the various distributor components to each other. Refer to the photo on page 9. Begin by checking the spade terminals, which are protected by plastic boots. The female spade terminals must fit tightly over the male terminals. If there’s any looseness present, remove the female terminals, then carefully squeeze them closed with a needle-nose pliers. Reinstall the female terminals, making certain they’re installed directly onto the male terminals, not next to them. The plastic boots can obscure your view, so make sure you’ve got them on right.

The ignition coil may have either spade or eyelet terminals, like the ones shown in the photo. Eyelet terminals can present their own set of problems. Make certain the machine screws are actually securing the eyelet terminals tightly in place. Substitution of the wrong machine screws may cause too-long screws to bottom out in the coil before they actually tighten down on the eyelet terminals. This may produce a connection that’s good enough to get the engine started most of the time, but that could cause an intermittent no-start the rest of the time. If the screws are too long, replace them with screws of the proper length.

Last of all, let’s talk about spark. Modern fuel-injected engines need a strong spark, especially during starting. As long as it’s receiving a signal indicating spark is being delivered, the PCM is going to continue commanding delivery of fuel to the cylinders via the injectors. It doesn’t necessarily know if it’s a strong spark or a weak spark—just that it’s a spark. It doesn’t take too many engine revolutions before the engine becomes flooded with unburned fuel, making it even more unlikely that the coil is going to be able to provide enough spark to wet plugs with too-wide gaps. The next step is a call for a tow truck.

A Honda engine like your customer’s may need 20 to 25kV to start and run. Ideally, ignition testing should be conducted with a secondary ignition oscilloscope or, at the very least, a dedicated spark tester. Holding a spark plug wire next to the block while cranking the engine is not enough to verify sufficient spark.

After disabling the engine’s ability to start by killing fuel delivery, you need to determine the maximum kV the coil is capable of delivering. A secondary ignition oscilloscope will show you peak coil kV during each ignition event, plus provide a wealth of additional information that will help you identify other weak components like worn plugs. The dedicated spark tester’s preset gap will force the coil to produce enough secondary voltage to jump the gap. If it can’t make it, it needs to be replaced.